Download or read book Entrainment and Deposition Rates of Droplets in Annular Two phase Flow PWR BWR written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The droplet entrainment from a liquid film is important to the mass, momentum, and energy transfer processes in annular two-phase flow. For example, the amount of entrainment as well as the rate of entrainment significantly affect the occurrences of the dryout, whereas the post CHF heat transfer depends strongly on the entrainment and droplet sizes. Despite the importance of the entrainment rate, there have been no satisfactory correlations available in the literature. In view of these, correlations for entrainment rate covering both entrance region and equilibrium region have been developed from a simple model in collaboration with data. Results show that the entrainment rate varies considerably in the entrainment development region, however, at a certain distance from an inlet it attains an equilibrium value. A simple approximate correlation has been obtained for the equilibrium state where entrainment rate and deposition rate becomes equal. The result indicates that the equilibrium entrainment rate is proportional to Weber number based on the hydraulic diameter of a tube.

Download or read book Evaluation of Droplets Deposition Coefficient and Entrainment Rate in Annular Two phase Flow in Vertical Round Tube written by Yiak Mong Yeoh and published by . This book was released on 1998 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation of Droplet Deposition Coefficient and Entrainment Rate in Annular Two Phase Flow vertical Flow written by Chee Hwa Danny Yeo and published by . This book was released on 1998 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanism and Correlation of Droplet Entrainment and Deposition in Annular Two phase Flow written by Isao Kataoka and published by . This book was released on 1982 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Droplet Entrainment Correlation for High Pressure Annular Two phase Flow written by and published by . This book was released on 1996 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: The amount of entrainment in annular flow is essential to predict the point of dryout. Most of the entrainment correlations available in the literature are obtained from air-water low pressure data. However many important industrial applications involve high pressure annular flows. There are very few correlations applicable in this range and they are solely based on empirical data fits. Comparing the low pressure entrainment data of Cousins and Hewitt (1968) and the high pressure data of Keeys et. al. (1970) and Wurtz (1978) with existing correlations, the agreement at high pressure is generally poor, except for the empirical correlation of Nigmatulin and Krushenok (1989) which depends on a Weber number that includes the droplet concentration. We propose a new semi-mechanistic entrainment correlation for fully developed annular flow conditions: E = (0.9642)/(1 + (3836/We{sub C})). It is developed based on the droplet continuity equation and the entrainment rate model of Dallman et. al. (1979). This model is then modified to introduce a Weber number that includes the droplet concentration, We{sub C}. This Weber number is shown to scale the available high and low pressure air-water and steam-water data better than the other definitions. Because the new correlation is based on a model of entrainment rate it may be used as a starting point in the development of a correlation for this process applicable to high pressure water-steam annular flows. A correlation is suggested pending validation with high pressure entrainment rate data. 12 refs., 11 figs.

Download or read book Interfacial Transfer in Annular Dispersed Flow PWR BWR written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The interfacial drag, droplet entrainment, droplet deposition and droplet-size distributions are important for detailed mechanistic modeling of annular dispersed two-phase flow. In view of this, recently developed correlations for these parameters are presented and discussed in this paper. The onset of droplet entrainment significantly alters the mechanisms of mass, momentum, and energy transfer between the film and gas core flow as well as the transfer between the two-phase mixture and the wall. By assuming the roll wave entrainment mechanism, the correlations for the amount of entrained droplet as well as for the droplet-size distribution have been obtained from a simple model in collaboration with a large number of data. Then the rate equations for entrainment and deposition have been developed. The drag correlations relevant to the droplet transfer is also presented. The comparison of the correlations to various data show satisfactory agreement.

Download or read book Liquid Phase Mass Transfer in Annular Two phase Flow written by L. B. Cousins and published by . This book was released on 1968 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Energy Research Abstracts written by and published by . This book was released on 1987 with total page 1284 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Entrainment Rate of Droplets in the Ripple annular Regime for Small Vertical Tubes written by and published by . This book was released on 1998 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-fluid model predictions of film dryout in annular flow are limited by the uncertainties in the constitutive relations for the entrainment rate of droplets from the liquid film. The main cause of these uncertainties is the lack of separate effects experimental data in the range of the operating conditions in nuclear power reactors. Air/water and Freon-113 entrainment rate data have been obtained in 10 mm tubes using the film extraction technique. These experiments have been scaled to approach high pressure steam-water flow conditions. The effects of surface tension and density ratio, missing from most previous data sets, have been systematically tested. The entrainment rate mechanism is assumed to be a Kelvin-Helmholtz instability. Based on this analysis and two previous correlations, a new correlation is proposed that is valid for low viscosity fluids in small ducts in the ripple annular regime.

Download or read book Boiling written by Yasuo Koizumi and published by Elsevier. This book was released on 2017-06-22 with total page 849 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boiling: Research and Advances presents the latest developments and improvements in the technologies, instrumentation, and equipment surrounding boiling. Presented by the Japan Society of Mechanical Engineers, the book takes a holistic approach, first providing principles, and then numerous practical applications that consider size scales. Through six chapters, the book covers contributed sections from knowledgeable specialists on various topics, ranging from outlining boiling phenomena and heat transfer characteristics, to the numerical simulation of liquid-gas two phase flow. It summarizes, in a single volume, the state-of-the-art in boiling heat transfer and provides a valuable resource for thermal engineers and practitioners working in the thermal sciences and thermal engineering. - Explores the most recent advancements in boiling research and technology from the last twenty years - Provides section content written by contributing experts in their respective research areas - Shares research being conducted and advancements being made on boiling and heat transfer in Japan, one of the major research hubs in this field

Download or read book Liquid Transfer and Entrainment Correlation for Droplet annular Flow PWR BWR written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A correlation for the amount of entrained liquid in annular flow has been developed from a simple model and experimental data. There are basically two different regions of entrainment, namely, the entrance and quasi-equilibrium regions. The correlation for the equilibrium region is expressed in terms of the dimensionless gas flux, diameter, cand total liquid Reynolds number. The entrance effect is taken into account by an exponential relaxation function. It has been shown that this new model can satisfactorily correlate wide ranges of experimental data for water. Furthermore, the necessary distance for the development of entrainment is identified. These correlations, therefore, can supply accurate information on entrainment which has not been available previously.

Download or read book An Experimental and Analytical Investigation of Entrainment Rates for Downward Annular Mist Two phase Flow in Pipes and Downstream of a Localized Contraction written by Kim Ann Shollenberger and published by . This book was released on 1994 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A model for the droplet deposition rate in horizontal annular two phase flow written by N. S. Wilkes and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Multiphase Flow Dynamics 5 written by Nikolay Ivanov Kolev and published by Springer Science & Business Media. This book was released on 2011-10-18 with total page 839 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present Volume 5 of the successful book package "Multiphase Flow Dynamics" is devoted to nuclear thermal hydraulics which is a substantial part of nuclear reactor safety. It provides knowledge and mathematical tools for adequate description of the process of transferring the fission heat released in materials due to nuclear reactions into its environment. It step by step introduces into the heat release inside the fuel, temperature fields in the fuels, the "simple" boiling flow in a pipe described using ideas of different complexity like equilibrium, non equilibrium, homogeneity, non homogeneity. Then the "simple" three-fluid boiling flow in a pipe is described by gradually involving the mechanisms like entrainment and deposition, dynamic fragmentation, collisions, coalescence, turbulence. All heat transfer mechanisms are introduced gradually discussing their uncertainty. Different techniques are introduced like boundary layer treatments or integral methods. Comparisons with experimental data at each step demonstrate the success of the different ideas and models. After an introduction of the design of the reactor pressure vessels for pressurized and boiling water reactors the accuracy of the modern methods is demonstrated using large number of experimental data sets for steady and transient flows in heated bundles. Starting with single pipe boiling going through boiling in the rod bundles the analysis of complete vessel including the reactor is finally demonstrated. Then a powerful method for nonlinear stability analysis of flow boiling and condensation is introduced. Models are presented and their accuracies are investigated for describing critical multiphase flow at different level of complexity. Basics of designing of steam generators, moisture separators and emergency condensers are presented. Methods for analyzing a complex pipe network flows with components like pumps, valves etc. are also presented. Methods for analysis of important aspects of the severe accidents like melt-water interactions, external cooling and cooling of layers of molten nuclear reactor material are presented. Valuable sets of thermo-physical and transport properties for severe accident analysis are presented for the following materials: uranium dioxide, zirconium dioxide, stainless steel, zirconium, aluminum, aluminum oxide, silicon dioxide, iron oxide, molybdenum, boron oxide, reactor corium, sodium, lead, bismuth, and lead-bismuth eutectic alloy. The emphasis is on the complete and consistent thermo dynamical sets of analytical approximations appropriate for computational analysis. Therefore the book presents a complete coverage of the modern Nuclear Thermal Hydrodynamics. This present second edition includes various updates, extensions, improvements and corrections. This present second edition includes various updates, extensions, improvements and corrections.

Download or read book Hydrodynamics of Annular dispersed Flow PWR BWR written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The interfacial drag, droplet entrainment, and droplet size distributions are important for detailed mechanistic modeling of annular dispersed two-phase flow. In view of this, recently developed correlations for these parameters are presented and discussed in this paper. The drag correlations for multiple fluid particle systems have been developed from a similarity hypothesis based on the mixture viscosity model. The results show that the drag coefficient depends on the particle Reynolds number and droplet concentration. The onset on droplet entrainment significantly alters the mechanisms of mass, momentum, and energy transfer between the film and gas core flow as well as the transfer between the two-phase mixture and the wall. By assuming the roll wave entrainment mechanism, the correlations for the amount of entrained droplet as well as for the droplet size distribution have been obtained from a simple model in collaboration with a large number of data.

Download or read book Droplets in Annular Two Phase Flow written by David Ruey-Chyi Chang and published by . This book was released on 1973 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Annular Two Phase Flow written by Geoffrey Hewitt and published by Elsevier. This book was released on 2013-10-22 with total page 327 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annular Two-Phase Flow presents the wide range of industrial applications of annular two-phase flow regimes. This book discusses the fluid dynamics and heat transfer aspects of the flow pattern. Organized into 12 chapters, this book begins with an overview of the classification of the various types of interface distribution observed in practice. This text then examines the various regimes of two-phase flow with emphasis on the regions of occurrence of the annular flow regime. Other chapters consider the single momentum and energy balances, which illustrate the differences and analogies between single- and two-phase flows. This book discusses as well the simple modes for annular flow with consideration to the calculation of the profile of shear stress in the liquid film. The final chapter deals with the techniques that are developed for the measurement of flow pattern, entrainment, and film thickness. This book is a valuable resource for chemical engineers.